Organosulfur compounds have a major role in advancing human health and well-being. A quarter of the most prescribed drugs contain sulfur, and sulfur is the most common heteroatom in all approved drugs after oxygen and nitrogen. The sulfur-containing functional groups also enable a variety of reactions that are used to synthesize natural products, biological probes, therapeutic agents, dyes, and advanced functional materials. However, the diverse and pluripotent reactivities of organosulfur compounds lead to low chemo-, regio- and stereoselectivities that adversely affect development of stereo- and regioselective approaches in organic synthesis. The long-term goal of this research is to advance the field of organic synthesis by streamlining synthetic access to centrally important organosulfur compounds and systematically developing their regio- and stereoselective transformations to broad classes of valuable functionalities and structural motifs. The intermediate oxidation state organosulfur reagents sulfinates have the potential to solve limitations of current methods of synthesis of organosulfur compounds and to enable new regio- and stereoselective reactions to a wide range of functionalized small molecules. However, there is a lack of efficient methods of synthesis of sulfinates directly from abundant precursors and a gap in fundamental understanding of the nearly entirely unexplored reactivity of sulfinates in the context of stereoselective C?C bond forming cross-coupling reactions The overall objective of this research is to develop methods of synthesis of sulfinates from abundant precursors and to develop regio- and stereoselective C?C bond forming reactions of sulfinates. This objective will be accomplished by systematically developing three research topics encompassing currently elusive synthetic methods. In the first part, stereodivergent catalytic cross-coupling reactions of intermediate sulfinates will be developed into a broad synthetic platform to access conjugated dienes and polyenes with high and predictable regio-and stereoselectivity. In the second part, a generic platform for harnessing abundant C?H bonds by means of a regioselective C?H sulfination will be developed. The third part is focused on catalytic alkene sulfination reactions to draw from abundance and reactivity of alkenes. Upon completion of this research program, a broad range of currently synthetically challenging functionalized molecules including sulfur-containing ones will become readily accessible for organic synthesis and drug discovery applications, contributing to improvement of human healthcare through more efficient syntheses of small molecule biological probes and therapeutic agents.